booya2000 Posted February 2, 2011 Posted February 2, 2011 I registered only to post this question as it's bothering me since yesterday. So.. I was watching Discovery Science and saw in a show that scientists are trying to send info in the past. A guy was saying that when this will be possible, they will be able to send messages back in time and prevent many major events that happened in history. Now this is where I don't understand it anymore. How come we didn't receive any message from the future? Our present and our past is the past of their future. Hope you understand what I mean. ( English not my natural language ) So how come all the major events still happened if "we" from the future didn't send any information back to the present ( past )? Or did they go "Oh let's not alter the history, it can be dangerous". Also, if the scientists will ever discover time traveling or sending info back in time, shouldn't we receive their test messages or something? For me, it doesn't seem normal that they discover, let's say in 50 years, the time machine and don't use it to send people back in time for research. Of course I don't expect to see someone on TV saying that he is from the future, and if I would I'd say that most probably he has problems. Sorry for repeating myself, as I said English is not my main language and I'm not a scientist. ( not even close to become one ) Anyway... what do you think?
ajb Posted February 2, 2011 Posted February 2, 2011 Now this is where I don't understand it anymore. How come we didn't receive any message from the future? It is expected that you can only send a message back in time only as far back as when the time machine was created. Thus, we will not get any messages until the machine is turned on. Our present and our past is the past of their future. Hope you understand what I mean. ( English not my natural language ) So how come all the major events still happened if "we" from the future didn't send any information back to the present ( past )? Another way out of this is to invoke "many worlds". When the message was sent back the Universe split up into (at least) two paths, one where the message was not received, which is the world we live in and a parallel world in which the message was received and acted up on. Or did they go "Oh let's not alter the history, it can be dangerous". Which is also another possibility. There is some kind of temporal agreement not to mess with the past. If time travel (to the past) is allowed in our Universe they we have to address these sort of questions as well others like causality. Right now there is a little evidence to show that time travel like this may not be allowed. Roughly, all proposed time machines seem to be quantum mechanically unstable. This may of course not be totally correct and there could be some way of creating time machines. The more mainstream research into time machines, also known as Closed Time-like Curves (CTCs) is all about pushing theories to the limit of breaking point. Doing so may give us hints into physics we do not know about yet, for example quantum gravity.
rktpro Posted February 2, 2011 Posted February 2, 2011 I think you can't go to past. You can go to future only. A one way travel. The same program showed this type of travel! Slowing down the time!
ajb Posted February 2, 2011 Posted February 2, 2011 I think you can't go to past. I believe that most physicists also think that. However, it is not absolutely clear that within the known laws of physics that time travel is forbidden. There is Hawking's chronology protection conjecture: The laws of physics do not allow the appearance of closed timelike curves. The conjecture is founded on semiclassical gravity. That is quantum field theory on a classical background space-time. Loosely, the aspects of the theory blow up to infinity when you get near a CTC. I am not aware of any general proof of this conjecture. I am also no aware of any counter examples. So to date, the conjecture seems well founded, but it may have loop holes.
Athena Posted February 2, 2011 Posted February 2, 2011 (edited) I love time travel stories, but I have a hard time believing in any reality other than the moment. I may be planning on attending a wedding, but if I am hit by a truck, I will not be at the wedding. My sense is, the future does not exist so we can not travel into the future. Same with the past. If the building I live in is burnt to the ground, it is gone. The past does not exist. Only if the building does not burn to the ground does it exist. If either the future of past exist, of what are they made? By the way, if the past does exist, that makes us all eternal doesn't it? How about this, ghosts are people stuck in time, and if we study ghost, we might be able to figure out how to move in time? Edited February 2, 2011 by Athena 1
steevey Posted February 3, 2011 Posted February 3, 2011 Time travel can't be possible as it would not only be a paradox, but also assume that for no apparent reason, the universe is recording every event. I guess if we were in some giant computer it would be possible, but you'd have to re-arrange every atom in the universe into a position and state it occupied before. Even then, you, the time traveler, would have to be unaware of anything. It also violates the conservation of matter and energy if everything isn't re-arranged. If you went back in time and saw yourself, then there would be infinite yous going back in time in the future, and for that to happen, matter would have to somehow get created.
Athena Posted February 3, 2011 Posted February 3, 2011 (edited) Time travel can't be possible as it would not only be a paradox, but also assume that for no apparent reason, the universe is recording every event. I guess if we were in some giant computer it would be possible, but you'd have to re-arrange every atom in the universe into a position and state it occupied before. Even then, you, the time traveler, would have to be unaware of anything. It also violates the conservation of matter and energy if everything isn't re-arranged. If you went back in time and saw yourself, then there would be infinite yous going back in time in the future, and for that to happen, matter would have to somehow get created. Can we explore that possible memory? I read a lot of information can be stored on a neutrino. If I remember correctly, light waves carry an image of what exist, and continue to carry that image even if what existed no longer exist. We understand how to electronically record information. How might the universe record a memory and maintain it? Would the memory manifest three dimensional material reality? Would there be any difference between the memory and the present manifest reality? Is all this not also a question of it ghost exist, and if we are eternal with our memories being as much a reality as our present? Is there a God who knows all and never forgets? Our own memories can be changed, but can the memory of the universe be changed? As you argued Steevey that would mean rearranging every atom. Or would it? I can rewrite my memory, but that doesn't change my body in away I can perceive the change. Is changing memory equal to changing matter? Edited February 3, 2011 by Athena
steevey Posted February 4, 2011 Posted February 4, 2011 (edited) Can we explore that possible memory? I read a lot of information can be stored on a neutrino. If I remember correctly, light waves carry an image of what exist, and continue to carry that image even if what existed no longer exist. We understand how to electronically record information. How might the universe record a memory and maintain it? Would the memory manifest three dimensional material reality? Would there be any difference between the memory and the present manifest reality? Is all this not also a question of it ghost exist, and if we are eternal with our memories being as much a reality as our present? Is there a God who knows all and never forgets? Our own memories can be changed, but can the memory of the universe be changed? As you argued Steevey that would mean rearranging every atom. Or would it? I can rewrite my memory, but that doesn't change my body in away I can perceive the change. Is changing memory equal to changing matter? You can't rewrite your memory. Your brain remembers whatever it remembers, which typically is things that occur every day or things that are useful to you. Changing a memory doesn't have anything to do with the universe. The memory contains specific arrays of chemicals and atoms in your brain. There was matter here before there was anything to have a memory, so memory shouldn't effect anything anyway. Light isn't really even a memory, it's just a photon with a specific wavelength and energy. Edited February 4, 2011 by steevey
IM Egdall Posted February 4, 2011 Posted February 4, 2011 Interestingly, we do experience time travel into the future all the time. It's just at our everyday speeds, the effect is so small we don't notice it. But iti s real. See:
The Apprentice Posted February 4, 2011 Posted February 4, 2011 How do any of us really know that we can't already time travel? I mean, the government would be in control of that stuff anyway, and there are things in History that we cant explain. I don't think this is the case, however: but its something to think about.
insane_alien Posted February 4, 2011 Posted February 4, 2011 How do any of us really know that we can't already time travel? I mean, the government would be in control of that stuff anyway, and there are things in History that we cant explain. I don't think this is the case, however: but its something to think about. governments have never been good at keeping juicy secrets. time travel would be huge, it would leak, there would be no way to keep it contained. also, the event of time travel would probably require ridiculous^silly amounts of energy. if there was a big massive power drain on the grid then THAT would have leaked and people would have found out about it.
steevey Posted February 4, 2011 Posted February 4, 2011 (edited) Interestingly, we do experience time travel into the future all the time. It's just at our everyday speeds, the effect is so small we don't notice it. But iti s real. See: Going into the future requires constant units of time to count at a faster rate than their standard constant duration. This does not happen every day. Every day, you measure things in seconds, and you constantly measure things only in the terms of seconds, or hours, or minutes, the duration of which is always the same throughout the day. A day never counts faster than a day, an hour never counts faster than an hour. How do any of us really know that we can't already time travel? I mean, the government would be in control of that stuff anyway, and there are things in History that we cant explain. I don't think this is the case, however: but its something to think about. We know because of logic and observation. Edited February 4, 2011 by steevey
alpha2cen Posted February 5, 2011 Posted February 5, 2011 (edited) Biological time machine(frozen human) is more energy saving than physical time machine. Can we regenerate the electromagnetic waves in the frozen human brain? Edited February 5, 2011 by alpha2cen
steevey Posted February 5, 2011 Posted February 5, 2011 Biological time machine(frozen human) is more energy saving than physical time machine. Can we regenerate the electromagnetic waves in the frozen human brain? We haven't figured out how to do that since some chemicals are broken down in the process and there isn't a known way to restart everything, such as the cell cycle and replication of DNA, motor functions, consciousness, or even a beating heart which can sustain itself.
lemur Posted February 5, 2011 Posted February 5, 2011 Just assume for a moment that not only is the speed of light relative to its context of emission, but that molecular motion was always relative to its inertial frame. In that case, gravity and other forces could ensure that matter remains intact as it exceeds the speed of light. Then, objects could travel faster than the light they emitted, which would allow them to precede the arrival of their history and thus exist in their own past from the perspective of their observer.
IM Egdall Posted February 5, 2011 Posted February 5, 2011 Just assume for a moment that not only is the speed of light relative to its context of emission, but that molecular motion was always relative to its inertial frame. In that case, gravity and other forces could ensure that matter remains intact as it exceeds the speed of light. Then, objects could travel faster than the light they emitted, which would allow them to precede the arrival of their history and thus exist in their own past from the perspective of their observer. YA, but the speed of light is not relative to its context of emission; it's always the same (in vacuum). Or am I missing something here?
lemur Posted February 5, 2011 Posted February 5, 2011 YA, but the speed of light is not relative to its context of emission; it's always the same (in vacuum). Or am I missing something here? The only thing you seem to be missing is that a thread about the possibility of time travel would, I think, be impossible if everyone stuck to the idea that nothing can travel faster than light/energy propagation. That's why the only response I could think of that would facilitate time travel would be if somehow objects could move faster than light, e.g. if light's speed was relative to its source and thus different sources could travel faster than each other's light. Even if that was the case, though, how could two objects ever meet in close proximity in each other's past? As you get closer to an object, you get closer to its present, right? Presence = present?
TonyMcC Posted February 5, 2011 Posted February 5, 2011 What do we mean by time travel? Do we mean "I would like to be in this place in (say) 100 years from now?" If so, where will "this place" actually be in an expanding universe where everything including this world is constantly moving?
steevey Posted February 5, 2011 Posted February 5, 2011 (edited) What do we mean by time travel? Do we mean "I would like to be in this place in (say) 100 years from now?" If so, where will "this place" actually be in an expanding universe where everything including this world is constantly moving? Position is a term which is relative to a specific object or region. You can say "I would like to be in this place (relative to the Earth) 100 years from now" and still be in a defined location since Earth itself will still be Earth. Edited February 5, 2011 by steevey
lemur Posted February 5, 2011 Posted February 5, 2011 Position is a term which is relative to a specific object or region. You can say "I would like to be in this place (relative to the Earth) 100 years from now" and still be in a defined location since Earth itself will still be Earth. But if you could somehow just get all your particles to "blink" for 100 years, during which time they would cease to have momentum or be pulled or pushed by any force, where would you be when you re-appeared? Think of the galaxy as a vehicle and your "blink" was relative to some medium that the galaxy was traveling through. You might re-appear very far from Earth.
TonyMcC Posted February 5, 2011 Posted February 5, 2011 (edited) Steevey - Souds a bit like you are making a fixed earth the centre of a rotating universe. Even a Galileo would have to think about that. Edited February 5, 2011 by TonyMcC
steevey Posted February 5, 2011 Posted February 5, 2011 (edited) But if you could somehow just get all your particles to "blink" for 100 years, during which time they would cease to have momentum or be pulled or pushed by any force, where would you be when you re-appeared? Think of the galaxy as a vehicle and your "blink" was relative to some medium that the galaxy was traveling through. You might re-appear very far from Earth. Even in contemporary sci-fi travel, matter doesn't "blink" out of existence while you time travel, its that the time traveler that is preserved while the rest of matter is still going about. If you stood in one spot on the Earth for 100 years, you'd still be in whatever position you were in before, assuming the Earth hasn't been destroyed. Steevey - Souds a bit like you are making a fixed earth the centre of a rotating universe. Even a Galileo would have to think about that. Like I said, position is relative to an object or region. It doesn't matter if I keep mentioning Earth, there are likely many other planets life could have been on where I could have made the same logical argument. But, since life is based on Earth and not much of it travels outside the realm of Earth, the main thing to compare locations to is Earth. Edited February 5, 2011 by steevey
lemur Posted February 5, 2011 Posted February 5, 2011 Even in contemporary sci-fi travel, matter doesn't "blink" out of existence while you time travel, its that the time traveler that is preserved while the rest of matter is still going about. If you stood in one spot on the Earth for 100 years, you'd still be in whatever position you were in before, assuming the Earth hasn't been destroyed. Let me get this straight - you are insisting that one approach to fiction is more reasonable than another on the basis of citing "contemporary sci-fi travel?" That is like saying that it's foolish to imagine teleporting could occur without a brightly colored aura and electronic sound-effects because that's what happens when you beam up on Star Trek.
HamsterPower Posted February 5, 2011 Posted February 5, 2011 wow this post helped me understand a lot
steevey Posted February 6, 2011 Posted February 6, 2011 Let me get this straight - you are insisting that one approach to fiction is more reasonable than another on the basis of citing "contemporary sci-fi travel?" That is like saying that it's foolish to imagine teleporting could occur without a brightly colored aura and electronic sound-effects because that's what happens when you beam up on Star Trek. The approach is just yours, and doesn't makes sense to me. The sci-fi ones not only makes sense to me, but are used more often which means more people agree on it as well.
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